package three;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNextInt()) {
            int a = in.nextInt();

            int sum = 0;
            while (a % 10 != 0) {
                sum += a % 10;
                a /= 10;
            }

            System.out.println(sum);
        }
    }
}
